This invention relates to cartridges having an endless inked ribbon contained therein and means for translating the ribbon from an exit slot past a print station and through an entrance slot into the interior thereof.
Inked ribbon cartridges are known which supply an endless inked ribbon to a printing station of an associated printing device, e.g. a rotary printer or a typewriter. In typical devices of this type, a large quantity of the ribbon is normally contained within the cartridge in an interior ribbon chamber defined by boundary walls having an entrance protion and an exit portion, with the boundary walls arranged at least partially interior of the side walls of the cartridge. The ribbon is typically arranged within the ribbon chamber in random folds and a loop is formed which extends from the boundary wall exit portion through the cartridge wall exit slot, past the external printing station, through the cartridge wall entrance slot and through the boundary wall entrance portion back into the ribbon chamber. A capstan and pinch roller is customarily provided adjacent the entrance to the ribbon chamber, with the capstan being driven by an external drive mechanism to provide a pulling force for translating the ribbon from the ribbon chamber along the loop path and back into the ribbon chamber. As the ribbon is translated in this manner, the ribbon migrates across the ribbon chamber and the random ribbon folds change shape, with new folds appearing adjacent the boundary wall entrance portion and folds adjacent the boundary wall exit portion disappearing.
In order to maintain the print quality of the characters printed at the external station substantially uniform, the tension of that portion of the inked ribbon located in the printing station must be maintained relatively constant in order to preclude stretching or contracting of this portion of the ribbon. This is typically achieved by providing a tensioning member either exterior of the cartridge, or internally thereof. Interior tensioning mechanisms employed in the past for this purpose include a spring blade member positioned adjacent the exit portion of the boundary walls for biasing the exiting ribbon against an edge surface. In addition, known cartridges have also employed two such spring members for this purpose, one located at the boundary wall exit portion and another located at the cartridge wall exit slot.
In order to function properly, the endless ribbon must be fed back into the ribbon chamber in such a manner that the random folds are free to migrate across the chamber from the boundary wall entrance portion to the boundary wall exit portion without snarling or tangling. Problems have been encountered, however, with known devices using a capstan and pinch roller for drawing the ribbon into the ribbon chamber with fouling of the ribbon usually occurring in the region of the capstan and pinch roller. While attempts have been made to find a solution to this problem, such attempts have not been uniformly satisfactory, since such solutions require the use of additional parts which greatly increase the manufacturing cost of the cartridge. Since an endless inked ribbon cartridge is normally designed as a disposable item, the device should preferably embody a minimum number of working elements in order to maintain the manufacturing costs at a minimum, while at the same time, providing trouble-free operation. To date, efforts to design a low cost endless inked ribbon cartridge meeting the above criteria have not met with wide success.